Semiconductor storage device and method for manufacturing semiconductor storage device

ABSTRACT

A semiconductor storage device includes first wiring layers stacked along a first direction, a first pillar including a first semiconductor layer and extending along the first direction through the first wiring layers, a second wiring layer disposed above the first pillar in the first direction and extending along a second direction perpendicular to the first direction, a semiconductor-containing layer including a first portion disposed on an upper end of the first pillar in the first direction, a second portion contacting the first portion and formed along the second wiring layer, and a third portion contacting an upper end of the second portion and extending along a third direction perpendicular to the first direction and crossing the second direction, and a first insulating layer between each of the first and second portions of the semiconductor-containing layer and the second wiring layer. An upper surface of the third portion contains a metal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2020-153733, filed on Sep. 14, 2020, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to semiconductor storagedevices and methods for manufacturing the semiconductor storage devices.

BACKGROUND

A NAND flash memory in which memory cells are three-dimensionallystacked is known.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a circuit configuration of asemiconductor storage device according to a first embodiment.

FIG. 2 is a circuit diagram of a memory cell array of a semiconductorstorage device according to a first embodiment.

FIG. 3 is a plan view of a memory cell array of a semiconductor storagedevice according to a first embodiment.

FIG. 4 is a cross-sectional view of a memory cell array of asemiconductor storage device according to a first embodiment.

FIG. 5 is a cross-sectional view of a memory cell array of asemiconductor storage device according to a first embodiment.

FIG. 6 is a perspective view of a select transistor of a memory cellarray of a semiconductor storage device according to a first embodiment.

FIGS. 7-18 are diagrams illustrating aspects of a method formanufacturing a semiconductor storage device according to a firstembodiment.

FIG. 19 is a cross-sectional view of a memory cell array of asemiconductor storage device according to a Modified Example 1.

FIG. 20 is a cross-sectional view of a memory cell array of asemiconductor storage device according to a Modified Example 2.

FIG. 21 is a cross-sectional view of a memory cell array of asemiconductor storage device according to a Modified Example 3.

DETAILED DESCRIPTION

Embodiments provide a semiconductor storage device having a low channelcontact resistance.

In general, according to one embodiment, a semiconductor storage deviceincludes a plurality of first wiring layers stacked along a firstdirection, a first pillar including a first semiconductor layer andextending along the first direction through the plurality of firstwiring layers, a second wiring layer disposed above the first pillar inthe first direction and extending along a second direction perpendicularto the first direction, and a semiconductor-containing layer. Thesemiconductor-containing layer includes a first portion disposed on anupper end of the first pillar in the first direction, a second portioncontacting the first portion and formed along the second wiring layer,and a third portion contacting an upper end of the second portion andextending along a third direction perpendicular to the first directionand crossing the second direction. The semiconductor storage devicefurther includes a first insulating layer between each of the first andsecond portions of the semiconductor-containing layer and the secondwiring layer. At least an upper surface of the third portion contains ametal.

Hereinafter, semiconductor storage devices according to certain exampleembodiments will be described with reference to the drawings. In thefollowing description, components having the same or similar functionsare denoted by the same reference numerals. Additional description ofrepeated components may be omitted after an initial explanation. Thedrawings are schematic or conceptual, and the depicted relationshipsbetween the thickness and width of each component, the ratio of thesizes between different components, and the like are not always the sameas the actual component. In this specification, the term a “connection”is not limited to the case of being physically connected, but alsoincludes the case of being electrically connected. In thisspecification, “extending in or along a direction” denotes that, forexample, the dimension in the direction of a component is larger thanthe smallest dimension among the sizes of the component in an Xdirection, a Y direction, and a Z direction described later.

The X direction, the Y direction, and the Z direction are defined fordescriptive convenience as follows. The X direction and the Y directionare directions substantially parallel to a surface of a semiconductorsubstrate 20 (refer to FIG. 4 ). The Y direction is a direction alongwhich a slit SLT extends. The X direction is a direction intersecting(for example, being substantially perpendicular to) the Y direction. TheZ direction is a direction intersecting the X direction and the Ydirection (for example, substantially perpendicularly) and going awayfrom the semiconductor substrate 20. However, these expressions are onlyfor the descriptive convenience and do not necessarily reference to thedirection of gravity. In this disclosure, the Z direction can also bereferred to as the “first direction”.

First Embodiment

FIG. 1 is a block diagram illustrating a system configuration of asemiconductor storage device 1. The semiconductor storage device 1 is anonvolatile semiconductor storage device such as a NAND flash memory.The semiconductor storage device 1 includes a memory cell array 10, acommand register 11, an address register 12, a sequencer 13, a drivermodule 14, a row decoder module 15, and a sense amplifier module 16.

The memory cell array 10 includes a plurality of blocks BLK0 to BLKn(where n is an integer of 1 or more). The block BLK is a set ofnonvolatile memory cell transistors MC0 to MC7 (refer to FIG. 2 ). Thememory cell array 10 has a plurality of bit lines and a plurality ofword lines. Each of the memory cell transistors MC0 to MC7 is connectedto one bit line and one word line. When each of the memory celltransistors MC0 to MC7 does not need to be particularly distinguished,the memory cell transistor may be referred to as a memory celltransistor MC. The detailed configuration of the memory cell array 10will be described later.

The command register 11 stores a command CMD received by thesemiconductor storage device 1 from a memory controller 2. The commandCMD includes, for example, an instruction for allowing the sequencer 13to execute a read operation, a write operation, an erase operation, andthe like.

The address register 12 stores address information ADD received by thesemiconductor storage device 1 from the memory controller 2. The addressinformation ADD includes, for example, a block address BA, a pageaddress PA, and a column address CA. For example, the block address BA,the page address PA, and the column address CA are used to select ablock BLK, a word line, and a bit line, respectively.

The sequencer 13 is a circuit configured to control the entireoperations of the semiconductor storage device 1. For example, thesequencer 13 controls the driver module 14, the row decoder module 15,the sense amplifier module 16, and the like based on the command CMDstored in the command register 11 to execute the read operation, thewrite operation, the erase operation, and the like.

The driver module 14 is a circuit configured to generate a voltage usedin the read operation, the write operation, the erase operation, and thelike. Then, the driver module 14 applies the generated voltage to asignal line corresponding to a word line selected based on, for example,a page address PA stored in the address register 12.

The row decoder module 15 is a circuit configured to select one blockBLK in the corresponding memory cell array 10 based on a block addressBA stored in the address register 12. Then, the row decoder module 15applies, for example, the voltage applied to the signal line by thedriver module to the selected word line in the selected block BLK.

In the write operation, the sense amplifier module 16 applies thevoltage to each bit line according to write data DAT received from thememory controller 2. In addition, in the read operation, the senseamplifier module 16 determines the data stored in the memory cell basedon the voltage of the bit line and transmits the determination result asread data DAT to the memory controller 2.

Communication between the semiconductor storage device 1 and the memorycontroller 2 conforms to, for example, a NAND interface standard. Forexample, in the communication between the semiconductor storage device 1and the memory controller 2, a command latch enable signal CLE, anaddress latch enable signal ALE, a write enable signal WEn, a readenable signal REn, a ready/busy signal RBn, and the input/output signalI/O are used.

The input/output signal I/O is, for example, an 8-bit length signal andmay include the command CMD, the address information ADD, the data DAT,and the like.

The command latch enable signal CLE is a signal indicating that theinput/output signal I/O received by the semiconductor storage device 1is a command CMD.

The address latch enable signal ALE is a signal indicating that thesignal I/O received by the semiconductor storage device 1 is addressinformation ADD.

The write enable signal WEn is a signal that instructs the semiconductorstorage device 1 to input the input/output signal I/O.

The read enable signal REn is a signal that instructs the semiconductorstorage device 1 to output the input/output signal I/O.

The ready/busy signal RBn is a signal that notifies the memorycontroller 2 of whether the semiconductor storage device 1 is in a readystate for accepting an instruction from the memory controller 2 or abusy state for not accepting an instruction.

The semiconductor storage device 1 and the memory controller 2 describedabove may make up one semiconductor device. As the semiconductor device,a memory card such as an SD card or a solid state drive (SSD) may beexemplified.

Next, the electrical configuration of the memory cell array 10 will bedescribed.

FIG. 2 is a diagram illustrating an equivalent circuit of the memorycell array 10. Here, only one block BLK is extracted for illustrationpurpose. The block BLK includes a plurality of (for example, four)string units SU0 to SU3.

Each of the plurality of NAND strings NS is associated with bit linesBL0 to BLm (m is an integer of 1 or more). Each of the NAND strings NSincludes, for example, the memory cell transistors MC0 to MC7 and selecttransistors ST1 and ST2.

The memory cell transistor MC includes a control gate and a chargestorage layer and stores data in a nonvolatile manner. Each of theselect transistors ST1 and ST2 is used to select the string unit SUduring various operations.

The memory cell transistor MC may be ametal-oxide-nitride-oxide-semiconductor (MONOS) type in which aninsulating film is used for the charge storage layer or an FG type inwhich a conductive layer is used for the charge storage layer.Hereinafter, the MONOS type will be described as an example.

In each of the NAND strings NS, a drain of the select transistor ST1 isconnected to the associated bit line BL, and a source of the selecttransistor ST1 is connected to one end of the memory cell transistorsMC0 to MC7 connected in series. In the same block BLK, gates of theselect transistors ST1 in the string units SU0 to SU3 are commonlyconnected to select gate lines SGD0 to SGD3, respectively. The selectgate lines SGD0 to SGD3 are connected to the row decoder module 15.

In each of the NAND strings NS, a drain of the select transistor ST2 isconnected to the other end of the memory cell transistors MC0 to MC7connected in series. In the same block BLK, a source of the selecttransistor ST2 is commonly connected to a source line SL, and a gate ofthe select transistor ST2 is commonly connected to a select gate lineSGS. The select gate line SGS is connected to the row decoder module 15.

The bit line BL commonly connects one NAND string NS in each of thestring units SU0 to SU3 in each block BLK. The source line SL iscommonly connected, for example, between the plurality of blocks BLK.

A set of the plurality of memory cell transistors MC connected to acommon word line WL in one string unit SU is referred to as, forexample, a cell unit CU. For example, the storage capacity of the cellunit CU including the memory cell transistors MC each of which stores1-bit data is defined as “one-page data”. The cell unit CU may have astorage capacity of two-page data or more according to the number ofbits of data stored in the memory cell transistor MC.

Furthermore, the circuit configuration of the memory cell array 10 inthe semiconductor storage device 1 is not limited to the configurationdescribed above. For example, the number of memory cell transistors MCand the select transistors ST1 and ST2 in each NAND string NS may be anynumber. The number of string units SU in each block BLK may be anynumber.

FIG. 3 is a plan view of the memory cell array 10 in the semiconductorstorage device 1. FIG. 3 is a plan view of one block BLK. Here, eightstring units SU0 to SU7 are provided in one block BLK. Furthermore, someparts of the insulating layer are omitted from the drawings for purposesof description.

As illustrated in FIG. 3 , the slit SLT is on each of the two sidesurfaces of the word line WL in the Y direction. The slit SLT extendsalong the X direction. In an embodiment, the select gate line SGS andthe word lines WL0 to WL7 are sequentially stacked on the semiconductorsubstrate 20 (refer to FIG. 4 ). Then, the slit SLT separates, forexample, the select gate line SGS and the word line WL for each blockBLK.

As illustrated in FIG. 3 , the string units SU0 to SU7 are arranged, forexample, along the Y direction. Each of the string units SU has aplurality of memory pillars MP. When the string units SU0 to SU7 are notbeing distinguished from one another in the description, the stringunits may be referred to as string units SU.

The memory pillar MP corresponds to the NAND string NS. The memorypillar MP has the memory cell transistors MC0 to MC7 and the selecttransistors ST2 in the NAND string NS. The memory pillar MP penetratesor passes through the select gate line SGS and the word lines WL0 to WL7and extends along the Z direction. The details of the structure of thememory pillar MP will be described later.

For example, each string unit SU has two memory pillar groups arrangedalong the Y direction. In each string unit SU, the plurality of memorypillars MP are arranged in a zigzag manner in the X direction. One blockBLK has a group of 16 rows of memory pillars extending along the Xdirection and arranged in the Y direction.

For example, a memory pillar MP1 of the string unit SU1 and a memorypillar MP2 of the string unit SU2 are adjacent to each other in the Ydirection. A memory pillar MP3 of the string unit SU2 and a memorypillar MP4 of the string unit SU3 are adjacent to each other in the Ydirection. A memory pillar MP5 of the string unit SU1 and a memorypillar MP6 of the string unit SU2 are adjacent to each other in the Ydirection. The memory pillar MP1 and the memory pillar MP5 are adjacentto each other in the X direction, and the memory pillar MP2 and thememory pillar MP6 are adjacent to each other in the X direction. In theX direction, the memory pillars MP3 and MP4 are disposed between thememory pillars MP1 (and MP2) and the memory pillars MP5 (and MP6). Inthe Y direction, the memory pillar MP3 is disposed between the memorypillar MP1 (and MP5) and the memory pillar MP2 (and MP6). In addition,in the Y direction, the memory pillars MP2 and MP6 are disposed betweenthe memory pillars MP3 and the memory pillars MP4. Furthermore, an arrayof the memory pillars MP may be set in any manner.

The select transistor ST1 is on each memory pillar MP. Then, the gatesof the plurality of select transistors ST1 of each string unit SU arecommonly connected to the select gate line SGD. When the select gatelines SGD0 to SDG7 are not being distinguished from one another in thedescription, the select gate lines may be referred to as a select gateline SGD. In the example of FIG. 3 , each of the select gate lines SGDis between the memory pillars MP adjacent in the Y direction and extendsalong the X direction. For example, in the string unit SU2, the selectgate line SGD2 extends along the X direction between the selecttransistor ST1 on the memory pillar MP3 and the select transistor ST1 onthe memory pillar MP2 (and MP6).

In the following description, for example, in the XY plane substantiallyparallel to the semiconductor substrate, the direction connecting thecenter of the memory pillar MP1 with the center of the memory pillar MP2is notated as an A direction, and the direction connecting the center ofthe memory pillar MP6 with the center of the memory pillar MP4 isnotated as a B direction. The A direction is a direction that issubstantially parallel to the semiconductor substrate and is differentfrom the X direction and the Y direction. The B direction is a directionthat is substantially parallel to the semiconductor substrate andintersects the A direction.

In an embodiment, in the two adjacent string units SU, the selecttransistors ST1 of the two memory pillars MP adjacent to each other inthe A direction or the B direction are commonly connected to one bitline BL via contact plugs CP1 and CP2. In other words, the two selecttransistors ST1 that are provided between the two select gate lines SGDand adjacent to each other in the A direction or the B direction arecommonly connected to one contact plug CP1.

For example, a semiconductor-containing layer 33 of the memory pillarMP1 of the string unit SU1 and the semiconductor-containing layer 33 ofthe memory pillar MP3 of the string unit SU2 adjacent to each other inthe A direction are connected to one contact plug CP1. Similarly, forexample, the semiconductor-containing layer 33 of the memory pillar MP6of the string unit SU2 and the semiconductor-containing layer 33 of thememory pillar MP4 of the string unit SU3 adjacent to each other in the Bdirection are connected to one contact plug CP1.

The contact plug CP2 is provided on the contact plug CP1. The contactplug CP2 connects any of the plurality of bit lines BL extending alongthe Y direction with the contact plug CP1.

FIG. 4 is a cross-sectional view of the memory cell array 10 in thesemiconductor storage device 1. FIG. 4 is a cross-sectional view takenalong the line A1-A2 of FIG. 3 .

As illustrated in FIG. 4 , an insulating layer 21 is formed on thesemiconductor substrate 20. The insulating layer 21 is formed by, forexample, a silicon oxide film (SiO₂). Furthermore, a circuit such as therow decoder module 15 or the sense amplifier module 16 may be providedin the region where the insulating layer 21 is formed, that is, betweenthe semiconductor substrate 20 and a wiring layer 22.

The wiring layer 22 extending along the X direction and functioning as asource line SL is formed on the insulating layer 21. The wiring layer 22is made of a conductive material, for example, an n-type semiconductor,a p-type semiconductor, or a metal material.

An insulating layer 23 is formed on the wiring layer 22. The insulatinglayer 23 is made of, for example, SiO₂.

A nine-layered wiring layer 24 that functions as the select gate lineSGS and word lines WL0 to WL7 and a nine-layered insulating layer 25 arealternately stacked on the insulating layer 23 from the lower layer. Theinsulating layer 25 is between the adjacent wiring layers 24.

The wiring layer 24 is made of a conductive material, for example, ann-type semiconductor, a p-type semiconductor, or a metal material. Here,a stacked structure of titanium nitride (TiN) and tungsten (W) is usedas the wiring layer 24. Titanium nitride (TiN) has a function as abarrier layer for preventing a reaction between W and SiO₂ or as anadhesion layer for improving the adhesion of W when a film of W isformed by chemical vapor deposition (CVD). In addition, the insulatinglayer 25 includes, for example, SiO₂.

The memory pillar MP is in the stacked body of the wiring layer 24 andthe insulating layer 25. The bottom surface of the memory pillar MPpenetrates the nine-layered wiring layer 24 and reaches the wiring layer22. The memory pillar MP includes a block insulating film 26, a chargestorage layer 27, a tunnel insulating film 28, a semiconductor layer 29,a core layer 30, and a cap layer 31.

The memory pillar MP is in a hole that penetrates the plurality ofwiring layers 24 and the plurality of insulating layers 25, and itsbottom surface reaches the wiring layer 22. The block insulating film26, the charge storage layer 27, and the tunnel insulating film 28 arestacked in this order from the inner peripheral surface of the holetoward the inner side. The side surface of the semiconductor layer 29 isin contact with the tunnel insulating film 28, and the bottom surface ofthe semiconductor layer 29 is in contact with the wiring layer 22. Thesemiconductor layer 29 is a region where channels of the selecttransistor ST2 and the memory cell transistor MC are formed. Thesemiconductor layer 29 functions as a signal line connecting the currentpaths of the select transistor ST2 and the memory cell transistors MC0to MC7. The core layer 30 is located inside the semiconductor layer 29.The cap layer 31 of which side surface is in contact with the tunnelinsulating film 28 is on the semiconductor layer 29 and the core layer30, and the memory pillar MP includes the semiconductor layer 29penetrating the inner portions of the plurality of wiring layers 24 andextending along the Z direction.

The block insulating film 26, the tunnel insulating film 28, and thecore layer 30 are made of, for example, SiO₂. The charge storage layer27 is, for example, a silicon nitride film (SiN). The semiconductorlayer 29 and the cap layer 31 are made of, for example, polysilicon.

Each of the memory cell transistors MC0 to MC7 is formed by the memorypillar MP and the eight-layered wiring layer 24 functioning as each ofthe word lines WL0 to WL7. Similarly, the select transistor ST2 isformed by the memory pillar MP and the wiring layer 24 functioning asthe select gate line SGS.

Above the memory pillar MP, the select transistor ST1 is formed by thesemiconductor-containing layer 33, an insulating layer 34, and a wiringlayer 35. The channel region of the select transistor ST1 is a firstlayer 33 a and a second layer 33 b of the semiconductor-containing layer33 along the side surface and the bottom surface of the wiring layer 35.

The semiconductor-containing layer 33 has the first layer 33 a, thesecond layer 33 b, and a third layer 33 c. The semiconductor-containinglayer 33 electrically connects a conductor 37 described later with thesemiconductor layer 29.

The first layer 33 a extends along any direction in the XY plane. Thefirst layer 33 a extends in, for example, the Y direction. The firstlayer 33 a is between an upper end of the semiconductor layer 29 and abottom surface of the wiring layer 35. As illustrated in FIG. 4 , thecap layer 31 may be between the semiconductor layer 29 and the firstlayer 33 a. The second layer 33 b connects the first layer 33 a with thethird layer 33 c. The second layer 33 b extends from the first layer 33a along the substantially Z direction. The second layer 33 b is formedalong the side surface of the wiring layer 35. The third layer 33 c isin contact with the upper end of the second layer 33 b and extends alongany direction in the XY plane. The third layer 33 c extends along, forexample, the A direction or the B direction. The third layer 33 c isabove the upper surface of the wiring layer 35. The third layer 33 cconnects the two second layers 33 b that are in contact with the twomemory pillars MP adjacent to each other in the A direction or the Bdirection. The third layer 33 c connects the two adjacent selecttransistors ST1. The first layer 33 a and the second layer 33 b are madeof, for example, polysilicon or amorphous silicon.

FIG. 5 is a cross-sectional view of the memory cell array 10 in thesemiconductor storage device 1. FIG. 5 is an enlarged view of thesemiconductor-containing layer 33 of FIG. 4 . An upper surface 33 cA ofthe third layer 33 c further contains a metal in addition to asemiconductor material. The upper surface 33 cA of the third layer 33 cis made of, for example, a silicide. The silicide is a compound ofsilicon and a metal. The metal forming the silicide is, for example,nickel or cobalt. As illustrated in FIG. 5 , the third layer 33 c has,for example, a first region 33 c 1 and a second region 33 c 2. Thesecond region 33 c 2 is above the first region 33 c 1 in the Zdirection. The first region 33 c 1 is made of polysilicon or amorphoussilicon, and the second region 33 c 2 is made of a silicide.

The thickness of the third layer 33 c is, for example, larger than thethickness of the second layer 33 b. The thickness is a length of thelayer in the direction perpendicular to the plane along which the layerextends. The peripheral length of the upper surface 33 cA of the thirdlayer 33 c is, for example, equal to or larger than the peripherallength of a lower surface 33 cB. When the thickness of the third layer33 c is large, the third layer 33 c is prevented from being penetratedwhen the opening is formed to form the conductor 37. The volume of thesemiconductor expands when the semiconductor is combined with a metal(for example, silicided). The thickness of the third layer 33 c becomeslarger than the thickness of the second layer 33 b due to thecombination with the metal. The thickness of the third layer 33 c may beallowed to be larger than the thickness of the second layer 33 b byselectively growing the semiconductor on the third layer 33 c.

The insulating layer 34 is between the semiconductor-containing layer 33and the wiring layer 35. The insulating layer 34 is formed along thesemiconductor-containing layer 33. The insulating layer 34 functions asa gate insulating film of the select transistor ST1. The insulatinglayer 34 includes, for example, a first portion on the first layer 33 aand a second portion on the second layer 33 b. That is, the insulatinglayer 34 has, for example, the first portion extending along the Ydirection and the second portion of the second layer 33 b extendingalong the substantially Z direction. The insulating layer 34 is made of,for example, SiO₂. Furthermore, the insulating layer 34 may have astacked structure or, for example, a MONOS structure capable ofcontrolling a threshold value (more specifically, a stacked structure ofan insulating layer, a charge storage layer, and an insulating layer).

The wiring layer 35 is above the memory pillar MP. The wiring layer 35functions as the select gate line SGD. The wiring layer 35 extendsalong, for example, the X direction. For example, the center position ofthe wiring layer 35 is different from the center position of the memorypillar MP in the Y direction (see FIG. 6 ). The wiring layer is disposedabove the upper end of the semiconductor layer 29 in the Y direction.The wiring layer 35 is made of a conductive material, for example, ann-type semiconductor, a p-type semiconductor, or a metal material. Thewiring layer 35 has, for example, a single-layer structure of W or astacked structure of TiN/W. The wiring layer 35 may be made of asilicide.

Above the memory pillar MP, an insulating layer 32 extending along the Xand Y directions is formed between the layers of the insulating layer25. The insulating layer 32 functions as an etching stopper whenprocessing a trench TR (that is, a groove pattern). The insulating layer32 is made of an insulating material that has a high etch selectivity inetching as compared to the insulating layer 25 is used. The insulatinglayer 32 is made of, for example, SiN. In some examples, the insulatinglayer 32 may be omitted. The trench TR penetrates the insulating layers25 and 32 so that the bottom surface thereof reaches the memory pillarMP, and the trench TR extends along the X direction. The wiring layer 35is formed in the trench TR.

The semiconductor-containing layer 33 and the insulating layer 34 arestacked on the side surface and the bottom surface of the trench TRabove the memory pillar MP. An insulating layer 36 is formed in the sidesurface and the bottom surface of the trench TR excluding the regionwhere the semiconductor-containing layer 33 and the insulating layer 34are provided and in the region between the upper surfaces of the twotrenches TR adjacent to each other in the Y direction. The insulatinglayer 36 is made of, for example, SiO₂. The height of the upper surfaceof the wiring layer 35 in the Z direction is lower than that of theupper surface of the trench TR (that is, closer to the semiconductorsubstrate 20). That is, the height of the upper surface of the wiringlayer 35 in the Z direction is smaller than that of the upper surfacesof the semiconductor-containing layer 33 and the insulating layer 34.Furthermore, the insulating layer 36 provided in the region between theupper surfaces of the two trenches TR adjacent to each other in the Ydirection may be omitted in some examples.

The conductor 37 that functions as a contact plug CP1 is formed on thethird layer 33 c. The conductor 38 that functions as a contact plug CP2is formed on the conductor 37. A wiring layer 39 that functions as a bitline BL and extends along the Y direction is formed on the conductor 38.The conductors 37 and 38 and the wiring layer 39 are made of aconductive material, for example, a metal material.

Next, an example of the arrangement of the select transistor ST1 and theselect gate line SGD will be described with reference to FIG. 6 . FIG. 6is a perspective view illustrating the arrangement of the upper portionof the memory pillar MP, the select transistor ST1, the select gate lineSGD, the contact plugs CP1 and CP2, and the bit line BL. Furthermore, inthe example of FIG. 6 , the insulating layer is not fully illustratedfor simplifying the description. In addition, the details of the selecttransistor ST1 are not illustrated.

As illustrated in FIG. 6 , for example, the two memory pillars MP1 andMP3 are arranged along a line that is inclined with respect to the Xdirection and the Y direction. The wiring layer 35 (corresponding toselect gate line SGD1) extends along the X direction so as to pass abovethe memory pillar MP1. Similarly, the wiring layer 35 (corresponding toselect gate line SGD2) extends along the X direction so as to pass abovethe memory pillar MP3. A wiring layer 35 is not provided between thememory pillar MP1 and the memory pillar MP3. Thesemiconductor-containing layer 33 and the insulating layer 34 are on thememory pillars MP1 and MP3 and between the memory pillar MP1 and thememory pillar MP3. The semiconductor-containing layer 33 is connected tothe wiring layer 39 via the conductors 37 and 38. Furthermore, in orderto illustrate the connection between the semiconductor-containing layer33 and the conductor 37, the insulating layer 25 between the memorypillar MP1 and the memory pillar MP3 is omitted from the depiction inFIG. 6 .

Next, a method of manufacturing the semiconductor storage device 1 willbe described. FIGS. 7 to 18 illustrate a plane of the memory cell array10 in the manufacturing process and a cross section (a B1-B2 crosssection) along the B1-B2 line.

Hereinafter, as a method for forming the wiring layer 24, a method inwhich a structure corresponding to the wiring layer 24 is formed byinitially using a sacrificial layer, and then the sacrificial layer isremoved and replaced with a conductive material (corresponding to wiringlayer 24) will be described.

As illustrated in FIG. 7 , the insulating layer 21, the wiring layer 22,and the insulating layer 23 are sequentially formed on the semiconductorsubstrate 20. Next, a nine-layered sacrificial layer 40 corresponding tothe wiring layer 24 and the nine-layered insulating layer 25 arealternately stacked. For the sacrificial layer 40, a material that has ahigh etch selectively in wet etching as compared to the insulating layer25 is used. The sacrificial layer 40 is made of, for example, SiN.

Next, the memory pillar MP is formed. First, a hole which penetrates thenine-layered insulating layer 25, the nine-layered sacrificial layer 40,and the insulating layer 23 and in which the bottom surface reaches thewiring layer is formed. Next, the block insulating film 26, the chargestorage layer 27, and the tunnel insulating film 28 are sequentiallystacked. After that, the block insulating film 26, the charge storagelayer 27, and the tunnel insulating film 28 on the bottom surface of thehole are removed to expose the wiring layer 22 on the bottom surface ofthe hole. Next, the semiconductor layer 29 and the core layer 30 areformed, and the inner portion of the hole is buried. Next, thesemiconductor layer 29 and the core layer 30 on the uppermost insulatinglayer 25 are removed. At this time, the semiconductor layer 29 and thecore layer 30 at the upper portion of the hole are also removed. Next,the cap layer 31 is formed so as to bury the upper portion of the hole.

As illustrated in FIG. 8 , after the insulating layer 25 is formed, theinsulating layer 32 is formed so as to cover the upper surface of thememory pillar MP. At this time, the insulating layer 32 is removed inthe region where the slit SLT is to be formed later. Next, theinsulating layer 25 is formed on the insulating layer 32.

As illustrated in FIG. 9 , the trench TR of which the bottom surfacereaches the memory pillar MP is formed. At this time, by using, forexample, the insulating layer 32 as an etching stopper, the trench TRmay be processed in two steps to reduce the processing damage to theupper surface of the memory pillar MP. In the bottom portion of thetrench TR, a portion of the upper surface of each of the memory pillarsMP arranged in two rows in a zigzag manner is exposed.

Next, the semiconductor-containing layer 33, an insulating layer 34A,and an insulating layer 41 are sequentially stacked. The insulatinglayer 41 functions as, for example, a protective layer of the insulatinglayer 34A. For the insulating layer 41, for example, a material that hasa high etch selectivity in wet etching as compared to the insulatinglayer 34A is used. The insulating layer 41 is made of, for example, SiN.

Next, as illustrated in FIG. 10 , a mask pattern covering the upperportions of the two adjacent memory pillars MP is formed between the twotrenches TR.

As illustrated in FIG. 11 , for example, the insulating layer 34A andthe insulating layer 41 in the region not covered with resist 42 areremoved by chemical dry etching (CDE).

As illustrated in FIG. 12 , after removing the resist 42, a portion ofthe semiconductor-containing layer 33 is oxidized to form the insulatinglayer 36. At this time, the semiconductor-containing layer 33 in theregion of which surface is covered with the insulating layer 34A and theinsulating layer 41 is not oxidized. Furthermore, an end region of thesemiconductor-containing layer 33 of which surface is covered with theinsulating layer 34A and the insulating layer 41 may be oxidized. Then,for example, the insulating layer 41 is removed by wet etching.

As illustrated in FIG. 13 , an insulating layer 34B and an insulatinglayer 34C are stacked in this order on the insulating layers 34A and 36.The insulating layer 34B is made of, for example, silicon nitride, andthe insulating layer 34C is made of, for example, silicon oxide. Then,after stacking the conductive layer in the trench TR, the wiring layer35 is formed by etching back the unnecessary portion.

As illustrated in FIG. 14 , the insulating layers 34A, 34B, and 34Cstacked on the upper surface of the semiconductor-containing layer 33are removed to expose the upper surface of the semiconductor-containinglayer 33. A portion of each of the insulating layers 34A, 34B, and 34Cis removed by, for example, chemical mechanical polishing (CMP). Asemiconductor may be further selectively grown on the exposedsemiconductor layer-containing layer 33 to increase the thickness of thesemiconductor-containing layer 33.

As illustrated in FIG. 15 , a metal layer 43 is stacked on the uppersurface of the stacked body. The metal layer is made of, for example,nickel. After stacking the metal layer 43, the semiconductor and themetal are combined on the upper surface of the semiconductor-containinglayer 33 by heating the stacked body. For example, the exposed surfaceof the semiconductor-containing layer 33 is silicided. The process isreferred to as a salicide process. When the wiring layer 35 is made of asemiconductor, the wiring layer 35 is also silicided at the same time.After that, the metal layer 43 that has not been silicided is removed.

As illustrated in FIG. 16 , the insulating layer 25 is formed on theupper surface 33 cA of the semiconductor-containing layer 33. Theinsulating layers 34A, 34B, and 34C become the insulating layer 34.

As illustrated in FIG. 17 , after the slit SLT is processed, thesacrificial layer 40 is removed from the side surface of the slit SLT bywet etching to form an air gap AG.

As illustrated in FIG. 18 , next, after the air gap is buried by formingTiN and W, the TiN and the W formed in the slit SLT and on the uppermostinsulating layer 25 are removed, and the wiring layer 24 is formed.

As illustrated in FIG. 18 , next, the slit SLT is buried by theinsulating layer 44. Next, the conductor 37 of which the bottom surfaceis in contact with the semiconductor-containing layer 33 is formed.Next, after the insulating layer 25 is formed, the conductor 38 and thewiring layer 39 are formed.

Through the above-described processes, the semiconductor storage device1 is manufactured. The manufacturing processes illustrated herein areexamples, and thus, other processes may be added between the processesor adopted. In addition, although the example in which the wiring layer35 is silicided at the same time as the semiconductor-containing layer33 has been described, the wiring layer 35 may be, for example, astacked film of tungsten (W) or tungsten (W) and titanium nitride (TiN).In such a case, after reaching the state of FIG. 13 , an insulatinglayer is stacked on the wiring layer 35 to bury the trench TR. Afterthat, similarly to FIG. 14 , the insulating layers 34A, 34B, and 34Cstacked on the upper surface of the semiconductor-containing layer 33are removed to expose the upper surface of the semiconductor-containinglayer 33, and the semiconductor and the metal are combined with eachother on the upper surface of the semiconductor-containing layer 33.

In the semiconductor storage device 1, the upper surface 33 cA of thethird layer 33 c of the semiconductor-containing layer 33 contains ametal and is made of, for example, a silicide. The metal-containingregion on the upper surface 33 cA of the third layer 33 c prevents theopening from penetrating the third layer 33 c when the opening forforming the conductor 37 is formed. In addition, by combining the uppersurface 33 cA of the third layer 33 c with the metal in advance (that isperforming self-aligned silicidation), the contact resistance betweenthe third layer 33 c and the conductor 37 is reduced.

Modified Example 1

A Modified Example 1 of the semiconductor storage device 1 will bedescribed. FIG. 19 is a cross-sectional view of the memory cell array 10in the semiconductor storage device 1 according to the ModifiedExample 1. FIG. 19 is an enlarged view of the semiconductor-containinglayer 33. The Modified Example 1 has the same configuration as thesemiconductor storage device 1 according to the first embodiment exceptfor the differences described below.

The semiconductor-containing layer 33 has a first layer 33 a, a secondlayer 33 b, and a third layer 33 d. The configuration of the third layer33 d is different from that of the third layer 33 c of thesemiconductor-containing layer 33 according to the first embodiment. Inthe third layer 33 d, all the regions in the thickness direction containmetals. For example, the entire third layer 33 d in the thicknessdirection is combined with a metal, and thus, for example, the entirethird layer 33 d is a full silicide in which the entire portions aresilicided. The thickness of the third layer 33 d is, for example, largerthan the thickness 33 b of the second layer, and the peripheral lengthof an upper surface 33 dA of the third layer 33 d is, for example, equalto or larger than the peripheral length of a lower surface 33 dB.

The same effects as those described for the first embodiment can beobtained by Modified Example 1.

Modified Example 2

A Modified Example 2 of the semiconductor storage device 1 will bedescribed. FIG. 20 is a cross-sectional view of the memory cell array 10in the semiconductor storage device 1 according to Modified Example 2.FIG. 20 is an enlarged view of the semiconductor-containing layer 33.The Modified Example 2 has the same configuration as the semiconductorstorage device 1 according to the first embodiment except for thedifferences described below.

The semiconductor storage device according to the Modified Example 2 hasa metal layer 50 on the upper surface 33 cA of the third layer 33 c ofthe semiconductor-containing layer 33. The metal layer 50 contains, forexample, titanium, tantalum, and/or tungsten. As illustrated in FIG. 14, the metal layer 50 is formed by exposing the upper surface 33 cA ofthe third layer 33 c and, after that, performing selective growth on theexposed conductive surface. For the selective growth of the metal layer50, for example, an area selective atomic layer deposition (ALD) method,an electroless plating method, or the like may be used.

The same effects described above for the first embodiment can beobtained the Modified Example 2. In addition, by having the metal layer50, it is possible to further prevent the opening for forming theconductor 37 from penetrating the third layer 33 c. In addition,titanium, tantalum, and/or tungsten used for the metal layer 50 are lesslikely to cause contamination in the subsequent processes as comparedwith nickel and cobalt used for silicidation. For example, when nickeland cobalt are mixed in an etching apparatus used for processing theinsulating layer in subsequent processes, the nickel and the cobalt aredifficult to clean, but the titanium, the tantalum, and the tungsten areeasier to clean than the nickel and the cobalt.

Modified Example 3

A Modified Example 3 of the semiconductor storage device 1 will bedescribed. FIG. 21 is a cross-sectional view of the memory cell array 10in the semiconductor storage device 1 according to Modified Example 3.FIG. 21 is an enlarged view of the semiconductor-containing layer 33.The semiconductor memory according to Modified Example 3 has the sameconfiguration as the semiconductor storage device 1 according to thefirst embodiment except for the differences described below.

The Modified Example 3 has the metal layer 50 on the upper surface 33 dAof the third layer 33 d described above for Modified Example 1. Themetal layer 50 is otherwise the same as that of the Modified Example 2.

The same effects as those described for the first embodiment can beobtained by Modified Example 3.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of thedisclosure. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the disclosure.

What is claimed is:
 1. A semiconductor storage device, comprising: aplurality of first wiring layers stacked along a first direction; afirst pillar including a first semiconductor layer and extending throughthe plurality of first wiring layers in the first direction; a secondwiring layer disposed above the first pillar in the first direction andextending along a second direction perpendicular to the first direction;a semiconductor-containing layer including: a first portion disposed onan upper end of the first pillar in the first direction, a secondportion contacting the first portion and formed alongside the secondwiring layer, and a third portion contacting an upper end of the secondportion and extending along a third direction perpendicular to the firstdirection and crossing the second direction; and a first insulatinglayer between each of the first and second portions of thesemiconductor-containing layer and the second wiring layer, wherein atleast an upper surface of the third portion contains a metal, and thethird portion of the semiconductor-containing layer includes: a firstlayer that contains either polysilicon or amorphous silicon and a secondlayer that contains a silicide on the first layer.
 2. The semiconductorstorage device according to claim 1, further comprising: a metal layeron the first layer of the third portion of the semiconductor-containinglayer.
 3. The semiconductor storage device according to claim 1, whereina thickness of the third portion of the semiconductor-containing layeris larger than a thickness of the second portion of thesemiconductor-containing layer.
 4. The semiconductor storage deviceaccording to claim 1, wherein a peripheral length of an upper surface ofthe third portion of the semiconductor-containing layer is equal to orlarger than a peripheral length of a lower surface of the third portion.5. The semiconductor storage device according to claim 1, wherein thefirst pillar includes a cap layer at the upper end thereof, and the caplayer contacts the first semiconductor layer of the first pillar and thefirst portion of the semiconductor-containing layer.
 6. Thesemiconductor storage device according to claim 1, further comprising: abit line extending along a fourth direction perpendicular to both thefirst and second directions above the third portion of thesemiconductor-containing layer and electrically connected to the thirdportion of the semiconductor-containing layer.
 7. A semiconductorstorage device comprising: a plurality of first wiring layers stackedalong a first direction; a first pillar including a first semiconductorlayer and extending through the plurality of first wiring layers in thefirst direction; a second wiring layer disposed above the first pillarin the first direction and extending along a second directionperpendicular to the first direction; a semiconductor-containing layerincluding: a first portion disposed on an upper end of the first pillarin the first direction, a second portion contacting the first portionand formed alongside the second wiring layer, and a third portioncontacting an upper end of the second portion and extending along athird direction perpendicular to the first direction and crossing thesecond direction; a first insulating layer between each of the first andsecond portions of the semiconductor-containing layer and the secondwiring layer; and a first conductor electrically connected to an uppersurface of the third portion of the semiconductor-containing layer andextending along the first direction, wherein a peripheral length of theupper surface of the third portion is larger than a peripheral length ofan upper surface of the first conductor, and at least an upper surfaceof the third portion contains a metal.
 8. A semiconductor storage devicecomprising: a plurality of first wiring layers stacked along a firstdirection; a first pillar including a first semiconductor layer andextending through the plurality of first wiring layers in the firstdirection; a second wiring layer disposed above the first pillar in thefirst direction and extending along a second direction perpendicular tothe first direction; a semiconductor-containing layer including: a firstportion disposed on an upper end of the first pillar in the firstdirection, a second portion contacting the first portion and formedalongside the second wiring layer, and a third portion contacting anupper end of the second portion and extending along a third directionperpendicular to the first direction and crossing the second direction;a first insulating layer between each of the first and second portionsof the semiconductor-containing layer and the second wiring layer; asecond pillar extending along the first direction through the firstwiring layers and a third wiring layer formed above the second pillarand extending along the second direction, wherein thesemiconductor-containing layer further includes: a fourth portiondisposed on an upper end of the second pillar in the first direction,and a fifth portion contacting the third and fourth portions andextending along the third wiring layer between the third and fourthportions, and at least an upper surface of the third portion contains ametal.